Septic System Pollution Contributes to Disease Outbreaks

More research and funding is needed to help understand the severity

Louis Coronado repairs his water well in Stratford, California. Domestic wells, because they are not regulated, are vulnerable to contamination. Septic system pollution is the primary cause of disease outbreaks in the United States from drinking untreated groundwater. Click image to enlarge. Photo © Matt Black / Circle of Blue

By Brett Walton, Circle of Blue

Drip by drip, septic systems, both faulty units and those that pass inspection, are nurturing an undesirable gang of bacteria, parasites, viruses, nutrients, and other contaminants in groundwater, streams, and soil in the United States.

Septic pollution represents an under-the-radar threat to human health in a country in which public and regulatory attention is directed toward centralized wastewater treatment facilities, industrial complexes, and farms.

People often think, ‘What did I eat?’ and do not think about the source of their drinking water.”
Joan Brunkard,
Centers for Disease Control and Prevention

Septic systems — typically an underground tank to trap toilet waste and perforated piping to let the liquid percolate into the soil — are used by nearly one in five American households and countless businesses, churches, and summer camps as a cheap, low-tech means of sewage disposal in areas not served by municipal sewers. They are most common in New England and the South.

Not all systems are a problem but an unknown number are putting human health and well-being at risk. The number is unknown because there few requirements to report the data that would help researchers understand the links between septic waste, failing septic systems, and disease, and fewer studies that trace illnesses back to the source of contamination.

“Septic systems are an under-recognized cause of disease outbreaks,” said Jonathan Yoder, who leads the domestic water, sanitation, and hygiene epidemiology team at the Centers for Disease Control and Prevention.

Lack of Data Leaves Officials and Researchers in the Dark

As it exits the tank and soaks into soil, septic waste can introduce pathogens and pollutants that lead to vomiting and diarrhea, such as norovirus or cryptosporidium. In some cases, the waste also increases the risk of diseases that result from long-term exposure at low concentrations, such as exposure to nitrates, which interfere with the blood’s capacity to carry oxygen and can cause brain damage in infants.

Contaminants are spread in different manners, depending on soil and geology. Soil microbes generally do a sufficient job of removing bacteria from the waste, but the soil’s treatment capacity diminishes as more septic units crowd a parcel of land. Studies in Georgia and Wisconsin have noted that fecal bacteria in streams and groundwater increases in areas with dense clusters of septic systems.

Basic septic systems are not designed to remove other pollutants. Nitrogen, converted in the soil to nitrate, passes through largely untouched. In Suffolk County, New York, where more than 1 million people are on septic systems, 10 percent of residential wells sampled between 1997 and 2013 exceeded the federal drinking water standard for nitrate. Pharmaceutical compounds are a new area of concern, especially for fish and other aquatic species. Septic tanks do not break down pharmaceuticals.

Michigan Traverse City septic system pollution Concrete Service Carl Ganter Circle of Blue

A stack of new septic tanks sits at Concrete Service, in Traverse City, Michigan. Click image to enlarge. Photo © J.Carl Ganter / Circle of Blue

Families and businesses that use a private well for drinking water are most vulnerable to diseases spread by septic systems. More than 44 million people in the United States, roughly 14 percent of the population, use private wells, according to the U.S. Geological Survey.Private well owners are generally not required to report water use, treat the water, or have it tested for contaminants. The lack of reporting requirements puts these families at greater risk than those using municipal water, which is tested dozens of times per day. It is also an obstacle for researchers who are trying to understand the scope and severity of disease outbreaks that could be linked to septic systems, according to Joan Brunkard of the Centers for Disease Control and Prevention.

“There’s a huge burden of unreported disease with diarrhea, for example,” Brunkard told Circle of Blue. “A family may not put two and two together when there’s a sickness. People often think, ‘What did I eat?’ and do not think about the source of their drinking water.”

Yoder attributes the lack of data not only to the reliability of household reports but on inadequate government funding of state health agencies to investigate outbreaks.

“We ask ourselves daily how well we understand the root causes of outbreaks,” Yoder told Circle of Blue. “In some ways there are a lot of gaps. Every outbreak is investigated differently depending on state and local agency expertise. A real challenge is the decline in the budgets of state environmental health officials. That has an impact on their ability to do surveys to identify the source of an outbreak and on understanding its magnitude. It’s an ongoing challenge of resources, expertise, and guidance.”

The CDC produces a report every two years on disease outbreaks associated with drinking water. The report draws from case studies that have been logged in the CDC database. The authors note that, because of the data limitations that Yoder and Brunkard describe, the report does not reflect a true accounting of the number of outbreaks.

Families may not report a failing septic system for a host of reasons, according to a University of North Carolina study published in October in the American Journal of Public Health. Families fear that their home may be condemned if they notify authorities that their sewage is not properly treated or that they will be forced to make repairs they cannot afford. “There are a lot of [septic tanks] that are failing now that we don’t know about, and people just live with them,” one county health official told the researchers.

Circle of Blue contacted the Association of State and Territorial Health Officials, the organization that represents the country’s public health agencies, to ask about their capacity to link disease outbreaks to septic systems. Virgie Townsend, ASTHO spokesman, said the organization could not answer the question because septic system pollution “is not an issue [state agencies] have sought to address collectively, which are the issues that ASTHO addresses.”

More Studies Needed

Even the scientific community is lagging, according to Mark Borchardt, a U.S. Department of Agriculture microbiologist. Borchardt has published papers on microbial contamination of groundwater for more than a decade, and he was the lead author for one of the most rigorous investigations of a disease outbreak linked to septic system contamination. He sees a lot of interest in his previously published work, calling it a “hot topic,” but says funding for new research is scarce.

Septic issues are a contributor in a majority of untreated groundwater disease outbreaks.”
Jonathan Yoder,
Centers for Disease Control and Prevention

“There is very little research on groundwater contamination by septic systems that I’m aware of, at least in the United States,” Borchardt told Circle of Blue. “There is research into the design of septic systems but there is big gap in research on the human health effects.”

Borchardt helped trace the path of a norovirus outbreak at a Wisconsin restaurant to its source. A pipe fitting on the septic tank cracked in 2007, just three weeks after the restaurant opened. Liquid from the tank leaked out, coursed through the limestone aquifer, and poisoned the restaurant’s well, located downslope from the septic tank, 188 meters away. Two hundred eleven patrons and 18 staff members fell ill with vomiting and diarrhea, and six people required hospital treatment.

Though a case of diarrhea may seem only a nuisance, an unexpected illness can generate a cascade of unwanted consequences. A sick child forces a parent to arrange last-minute care or miss work to act as nurse. An unplanned visit to the doctor, or worse a hospital trip, may strain the budget of a poor family.

Results from other disease assessments indicate that septic systems ought to be monitored and studied more carefully. In 2013, the CDC looked at nearly four decades of data on disease outbreaks linked to drinking untreated groundwater. The data was drawn from 248 outbreaks that were reported to the CDC between 1971 and 2008. Of the 172 cases in which a source of contamination was determined, 67 percent were linked to a septic tank or an improperly designed well. Unlike disease outbreaks from surface water sources, which are declining, outbreaks from untreated groundwater have remained constant.

“Septic issues are a contributor in a majority of untreated groundwater disease outbreaks,” Yoder summarized.

A 2014 study by researchers at the Public Health Agency of Canada supports the CDC’s findings that septic systems are a significant factor in contamination of drinking water wells.

The researchers analyzed data from 55 individual studies of groundwater that was contaminated by intestinal and fecal bacteria. The studies, conducted between 1990 and 2013 in Canada and the United States, showed that septic tanks were the most common cause of contamination.

Though epidemiologists and public health officials desire more data to better understand the frequency of illnesses originating from septic pollution, they say that most of the outbreaks could be prevented with greater vigilance and oversight. Local and state regulators should enforce restrictions on the number of units per acre and the distance from waterbodies and ensure that tanks are placed in the right soil conditions. Homeowners should regularly clean, maintain, and test their systems.

“The out-of-sight, out-of-mind thinking is a concern,” Brunkard said. “It’s so critical to test frequently.”